Planetarium projection dome

ABSTRACT

A self-supporting planetarium projection dome constructed of a plurality of segments connected together to form a hemispherical dome. The segments include oppositely disposed marginal flanges which are connected together to form circumferentially extending joints. Arcuate cover strips in the form of T-shaped members are clamped between the marginal flanges of the joints to cover the joints and present a continuous interior dome surface for realistically reflecting projected celestial images.

United States Patent William T. Clark [72] lnventor 1,589,938 6/1926Burney 52/283 Jackson, Miss. 2,071,093 2/1937 Van Horn..... 52/81 [21]Appl. No, 834,050 2,078,471 4/1937 Tinnerman... 52/468 [22] Filed June17, 1969 2,195,655 4/1940 Mortenson 52/584 [45] Patented July 27, 19712,803,856 8/1957 Kofahl et a1. 52/584X [73] Assignee Observa-DomeLaboratories, Inc. 3,454,259 7/1969 Faulkner 35/425 PrimaryExaminer-Alfred C. Perham [54] PLANETARIUM PROJECTION DOMEAlt0rneysC1arenc-e A. OBrien and Harvey B. Jacobson 6 Claims,6 DrawingFigs.

[52] U.S.Cl 52/81,

35/42-5, 52/464, 52/467 52/584 ABSTRACT: A self-supporting planetariumprojection dome [51] Int. Cl E04b 1/32, tructed of a plurality ofsegments connected together to E04d 13/03 60gb 27/00 form ahemispherical dome. The segments include oppositely [50] Field of Search52/80,8 disposed marginal flanges which are connected together to 82,467,468, 493, 584, 464; 35/425 form circumferentially extending joints.Arcuate cover strips in the form of T-shaped members are clamped betweenthe [56] References Cited marginal flanges of the joints to cover thejoints and present a UNITED STATES PATENTS continuous interior domesurface for realistically reflecting 240,868 5/1881 Waters 52/81projected celestial images.

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I/// i l 4 /2 l PLANETARIUM PROJECTION DOME The present inventionrelates to hemispherical domes and more particularly to the constructionof planetarium projection domes.

Planetarium domes of the general nature described are frequentlyprovided with an exteriorly disposed skeletal structure to which ahemispherical shell is rigidly secured. Although this type ofconstruction results in a dome of high structural strength it willnevertheless be appreciated that such a mode of construction is timeconsuming, relatively expensive and unduly heavy. Excessive weight isundesirable because special requirements for supporting the dome must bemet. Further, because most dome structures are fabricated from adjacentpositioned arcuate segments, circuml'erentially extending joints areformed which create lines through reflected celestial images, therebydetracting from the realism of that image.

The present invention includes a lightweight dome construction wherearcuate segments include outwardly extending upright marginal flangeswhich are connected together to effect hemispherical construction.Further, peripheral cover strips are clamped between mating marginalflanges so that a smooth interior dome surface can be realized.

These together with other objects and advantages which will becomesubsequently apparent reside in the details of construction andoperation as more fully hereinafter described and claimed, referencebeing had to the accompanying drawings forming a part hereof, whereinlike numerals refer to like parts throughout, and in which:

FIG. 1 is a sectional view illustrating the interior of a projectiondome disposed above a planetarium projector.

FIG. 2 is a fragmentaryview taken at an angle along a plane passingthrough line 2-2 of FIG. 1.

FIG. 3 is a fragmentary transverse sectional view taken along a planepassing through section line 3-3 of FIG. 2.

FIG. 4 is a fragmentary radial view taken along a plane passing throughline 4-4 of FIG. 3. I

FIG. 5 isa view similar to that illustrated in FIG. 2 with the marginalflanges of adjacently positioned arcuate segments being shown asbuckling.

FIG. 6 is a partial sectional view illustrating a modified constructionofthe present invention.

Referring to the figures and more particularly FIG. 1 thereof, thepresent planetarium dome is generally indicated by reference numeral 10and is seen to be comprised of adjacently positioned arcuate panels orsegments 12 which may be characterized as gores having mutuallyconnected apex portions secured by a connector ring 14.

The lower edges of the gores are coplanar. Mounting flanges forming atension ring 16 are connected to the lower edge of the hemisphericalbody so that it may be suspended from cables 18 with the dome beingcompletely self-supporting when suspended or mounted at its lower end ona loadbearing wall. The lower tension ring 16 rigidities the lower endof the dome to enable it to be self-supporting. A planetarium projector20 is disposed vertically below ring 14 in the usual manner.

It is also contemplated that the dome can be fabricated in the form of ageodesic body having interconnected triangularshaped segments, geodesicin nature, or any other shape component which may be used to construct ahemispherical dome.

Referring to FIG. 2, the arcuate segments 12 are seen to includesmall-sized apertures or perforations 22 therein for rendering the domestructure lightweight and to impiove acoustical properties thereof.However, it will be noted that the apertures are of sufficiently smallsize so that they do not become visually apparent when an image isprojected on the interior surface of the dome.

FIG. 2 illustrates the ideal disposition of adjacently positionedmarginal flanges 24 associated with mating segments 12. The flanges aremore clearly illustrated in FIG. 3 wherein the flanges are shown to beupright and radially outwardly extending. The flanges are retained inparallel-spaced relation to permit the insertion of a cover strip 28therebetween for purposes to be made more clear hereinafter. Theconnection between the flanges 24 in FIG. 3 create a joint or seam whichif left uncovered would present an undesirable line through a reflectedprojector image on the inner surface of the dome as previouslyexplained.

In order to cover the joints created by the connected marginal flanges,the cover strip 28 is used to effect a continuous interior dome surfacewhich is preferably coated with a flat paint or the like to diffuseincident light while retaining a high reflectance capacity. In moredetail, the cover strip 28 includes an elongated arcuate web portion 30which is disposed between the parallel-spaced marginal flanges 24. Theweb portion 30 is clamped between the marginal flanges 24 by a suitablenumber of regularly spaced rivets or like fasteners 36 therebyeliminating fastener heads or rivet heads exposed to the interior of thedome. The cover strip 28 is seen to further include elongated headportion 32 perpendicularly and integrally attached to the web portion30. The head portion 32 is normally disposed to contact the inwardsurface of the dome along lateral areas immediately adjacent the jointformed by the marginal flanges 24. Thus, it is the head portion 32 whichcovers the joint. As seen in FIG. 4, in actual fabrication of the coverstrip 28, the head portion 32 includes apertures 34 therein of the samesize as the apertures 22 in the arcuatesegments. These apertures makethe dome appear virtually seamless.

FIG. 2 illustrates the disposition of the marginal flanges 24 underideal conditions. However, in actual construction of the device, due tothe deformation or buckling of sheet metal material as it undergoesfabrication, the marginal flanges 24 will buckle outwardly from oneanother between the points of connection and others as indicated by 36in FIG. 5. Thus, the head portion 32 ofcover strip 28 must beofsufflcient width to cover the vertical inaccuracies of fitting of themarginal flanges.

Although the discussion up to this point has been directed to a domestructure fabricated at the plant of manufacture it would be desirablein a great number ofinstances to be able to construct the dome from aprefabricated assembly at the point of destination. Such a fieldassembly is illustrated in FIG. 6 and indicated by 40 wherein there isshown two adjacently positioned arcuate segments 12 having upright andconfronting marginal flanges 24 identical to those previously described.Elongated arcuate plate members 42 are suitably attached to respectiveflanges 24 along the edge of intersection 46 between each marginalflange 24 and a respective segment 12. Further attachment is providedalong the outward edge 44 of each marginal flange 24. The attachment ofthe plate members to the flanges is provided during fabrication of thesegments. Two parallel-spaced rows of apertures are formed in the platemember 2 to permit the passage of appropriate bolt fasteners 48 and 50therethrough. It will be noted that the dual row of apertures are formedduring fabrication so that all that is required at the point of assemblyis to position the arcuate segments 12 adjacent one another forpermitting passage of the bolt fasteners 48 and 50 through appropriatealigned apertures. Before securing the bolt fasteners, a cover strip 28is inserted between the marginal flanges 24 and upon the tightening ofthe bolt fasteners, the cover strip is secured therebetween.

The outward ends of the connected plate members 42 are parallel andspaced with respect to one another. In order to effect a spacer betweenthe plate members 42, a shim 52 is inserted therebetween prior to thefastener of the bolts 48 and 50, the shim being secured upon thetightening of the fasteners.

The foregoing is considered as illustrative only of the principles ofthe invention. Further, since numerous modifications and changes willreadily occur to those skilled in the art, it is not desired to limitthe invention to the exact construction and operation shown anddescribed, and accordingly all suitable modifications and equivalentsmay be resorted to, falling within the scope ofthe invention.

What I claim as new is as follows:

l. A substantially hemispherical projection dome comprising a pluralityof adjacently positioned segments having a plurality of small apertures,each segment having exteriorly disposed upstanding marginal flanges,each marginal flange disposed in parallel-spaced relation to a flange ofanadjacent segment to form a joint, an elongated cover strip serving toform a continuous interior surface across the joints thereby enhancingthe reflecting characteristics of the interior dome surface, each coverstrip having a web portion clamped between mating parallel flanges ofeach joint, each cover strip also having a thin head portion forbridging the joint and including a plurality of apertures the same sizeas the apertures in the segments to effect formation of the continuousinterior dome surface which is virtually seamless in appearance underlow lightingconditions when a projector projects an image onto the innersurface of the dome, and means for fastening the web portion betweenassociated marginal flanges.

2. The structure as defined in claim 1 wherein said means for fasteningthe web portion includes plate means attached to the exterior surface ofeach marginal flange at each joint, the plate members being disposed inspaced parallel relation, and fastener means connected betweenassociated plate members for effecting the clamping of the web portionof the cover strip between the marginal flanges.

3. The structure as defined in claim 2 wherein the plate members havingoutwardly disposed edges, defining a void therebetween and shim means inthe void to retain the outer edges of the plates spaced apart.

4. The structure as defined in claim 1 wherein said fastener meansincludes a plurality of fasteners extending through the flanges and webportion of the cover strip thereby retaining the interior surface of thedome free offasteners.

5. A planetarium dome comprising a plurality of interconnected panelsforming a substantially hemispherical dome, and cover strips overlyingand concealing the joints between adjacent panels, said panels and coverstrips having a plurality of small apertures distributed throughout thearea thereof to provide a virtually seamless appearance on the interiorsurface of the dome.

6. The planetarium dome defined in claim 5 wherein the inner surface ofeach of said panels and the inner surface of the cover strip is providedwith a flat pain coating to diffuse incident light while retaining ahigh reflectance capacity to facilitate observation of an imageprojected onto the interior surface by a projector, each of said panelsand cover strips being perforated in the same pattern with theperforations being small whereby they do not become visually apparentwhen observing an image projected onto the inner surface of the dome bya projector thereby providing an inner surface for the dome whichappears to be virtually seamless when observing an image projected ontothe inner surface of the dome by under low lighting conditions.

1. A substantially hemispherical projection dome comprising a pluralityof adjacently positioned segments having a plurality of small apertures,each segment having exteriorly disposed upstanding marginal flanges,each marginal flange disposed in parallel-spaced relation to a flange ofan adjacent segment to form a joint, an elongated cover strip serving toform a continuous interior surface across the joints thereby enhancingthe reflecting characteristics of the interior dome surface, each coverstrip having a web portion clamped between mating parallel flanges ofeach joint, each cover strip also having a thin head portion forbridging the joint and including a plurality of apertures the same sizeas the apertures in the segments to effect formation of the continuousinterior dome surface which is virtually seamless in appearance underlow lighting conditions when a projector projects an image onto theinner surface of the dome, and means for fastening the web portionbetween associated marginal flanges.
 2. The structure as defined inclaim 1 wherein said means for fastening the web portion includes platemeans attached to the exterior surface of each marginal flange at eachjoint, the plate members being disposed in spaced parallel relation, andfastener means connected between associated plate members for effectingthe clamping of the web portion of the cover strip between the marginalflanges.
 3. The structure as defined in claim 2 wherein the platemembers having outwardly disposed edges, defining a void therebetweenand shim means in the void to retain the outer edges of the platesspaced apart.
 4. The structure as defined in claim 1 wherein saidfastener means includes a plurality of fasteners extending through theflanges and web portion of the cover strip thereby retaining theinterior surface of the dome free of fasteners.
 5. A planetarium domecomprising a plurality of interconnected panels forming a substantiallyhemispherical dome, and cover strips overlying and concealing the jointsbetween adjacent panels, said panels and cover strips having a pluralityof small apertures distributed throughout the area thereof to provide avirtually seamless appearance on the interior surface of the dome. 6.The planetarium dome defined in claim 5 wherein the inner surface ofeach of said panels and the inner surface of the cover strip is providedwith a flat pain coating to diffuse incident light while retaining ahigh reflectance capacity to facilitate observation of an imageprojected onto the interior surface by a projector, each of said panelsand cover strips being perforated in the same pattern with theperforations being small whereby they do not become visually apparentwhen observing an image projected onto the inner surface of the dome bya projector thereby providing an inner surface for the dome whichappears to be virtually seamless when observing an image projected ontothe inner surface of the dome by under low lighting conditions.